Reinforced concrete structures are well known in the art, and are used in a wide variety of applications including, without limitation, buildings, bridges, parking decks and other structures constructed of concrete. Many of these types of structures are comprised of post-tensioned concrete in which steel cables are stressed within the concrete member after the concrete has been poured and hardened. More specifically, prior to pouring the concrete, anchors are set and attached to the concrete form in such a manner that the anchors will be embedded in the concrete after it is poured and hardens and the forms are removed. Because the anchors are typically embedded within the member and not otherwise accessible once the concrete is poured, pocket formers are used to form a void or anchor cavity for accessing the anchors from the ends of the member after the concrete is poured. After the concrete is poured and hardens, the pocket formers are removed thereby leaving anchor cavities within the ends of the concrete member for accessing the anchors. As explained more fully below, the anchors have tapered wedge-receiving seats and passages through which the cables extend.
Prior to pouring the concrete, steel cables are also installed, preferably within polyethylene sheathing, inside the concrete forms that are used to form the concrete member. Inasmuch as concrete members typically exhibit desirable compression characteristics but undesirable tensile characteristics, the steel cables and associated sheathing are typically placed in the tensile zone of a concrete member to add strength thereto. As noted above, the steel cables extend through openings in the anchors and initially extend beyond the ends of the concrete member. The concrete is then poured into the concrete form, and permitted to harden to a specific design strength. As described more fully below, tapered wedges are also installed and partially seated in the tapered wedge-receiving seat of each anchor on each side of the reinforcing cable.
After the concrete has sufficiently hardened, a hydraulic jack or stressing ram is used to pull or tension the steel cables that extend outwardly from the anchors to a desired pressure and elongation. The presence of the sheathing allows the steel cables to move relative to the concrete. Therefore, the steel cables can be stressed without frictional resistance from the concrete, which effectively eliminates or reduces the tensile stresses in the concrete due to the stressing. While stressed, the steel cables are permanently attached to the anchors at the ends of the concrete structure through the use of the aforementioned wedges. In this manner, the tensile forces in the steel cables are permanently transferred to the concrete as a compressive force through the anchorage assemblies located at the ends of the concrete member.
More specifically, the wedges are driven into the space between the cable and the surrounding anchor that is known as the wedge-receiving seat. In a two piece wedge system, the wedges are preferably semi-cylindrical, tapered pieces of metal with teeth or other markings on their interior surface for clamping or biting into the cable as the stressing ram releases the cable, thereby preventing the cable from slipping back through the anchor and into the sheathing encased in the concrete member. Once all of the cables have been properly stressed, the ends of the cables are cut so that they no longer extend beyond the concrete member, the anchor pockets are grouted, and the ends of the concrete structure are encapsulated to protect the cables from the elements. While two piece wedge systems are used for most projects involving monostrand or multi-strand cables, three piece wedge systems are also known in the art and used in certain applications.
Failure to properly install and seat the wedges within the anchor may result in damage or failure of the cables and/or the concrete member, which decreases productivity and may also result in severe injury or death. Nonetheless, it can be challenging to properly align, install and seat the wedges within the anchor assembly. More specifically, given the matrix of cables typically involved, limited work space, and lack of line of sight, it can be difficult and time consuming for a worker to properly position himself to align, install and seat the wedges within the anchor. Furthermore, the difficult task of installing and seating wedges in a limited work environment with a limited line of sight into the anchor cavity is further complicated by the fact that this work is oftentimes accomplished by hand and/or with the use of bulky and elongated handheld tools such as the one disclosed in U.S. Pat. No. 6,240,699 to Scanlon, et. al.
For example, when the wedges are installed by hand, the installer must attempt to insert both wedges into the wedge receiving seat between the cable and the surrounding anchor at the same time and at the proper orientation, all while maneuvering/straddling a matrix of cables in a confined work environment. More specifically, proper installation of the wedges requires that the wedges be installed on each side of the cable such that the gaps between the two wedges are located at the twelve-o'clock and six-o'clock positions. This is oftentimes difficult for the worker to accomplish, as the worker typically cannot see into the anchor cavity created by the pocket-former and/or there may be other objects (e.g., cables, etc.) in the line of sight. This problem is particularly acute when the concrete member receiving the wedges is a beam, which could have thirty-six or more cables that need to be anchored and stressed within a confined space. Moreover, because the worker must use both hands to simultaneously insert the wedges into the space, the worker is not able to utilize one of his hands to secure himself to the work platform, which could result in the worker losing his balance and/or becoming injured. Additionally, even after a worker successfully inserts the wedges into the space, the worker must then use a prior art device, such as an elongated handheld ram, to partially seat said wedges within the anchor assembly, which can also be time consuming as well as frustrating.
Similar limitations and difficulties exist with respect to the device described in the '699 patent, which also requires the worker to use two hands to properly install and partially seat the wedges within the wedge receiving seat of the anchor. More specifically, the '699 patent discloses an elongated device in which the worker must first magnetically attach the wedges to one end of the device, and then position the device adjacent to the cable. The worker must then apply a longitudinal force to the device and the magnetically attached wedges along the cable and in the direction of the anchor cavity to partially install the wedges in the anchor, all of which must be accomplished without breaking the magnetic connection between the device and the wedges. If the magnetic connection is broken, the wedges will fall from the device and need to be retrieved before the process can be started anew. Once the wedges are partially installed in the anchor cavity, the worker is then required to use his or her other hand to repeatedly and reciprocally slide the hammer member along the shaft of the device to pound the wedges into place, all while supporting the weight of the overall device with the worker's first hand. Because the operation of the device requires the worker to use both of his hands, the worker is unable to use one of his hands to properly secure himself to the work platform, the failure of which could lead to serious injury or even death.
Moreover, given the overall size of the device taught by the '699 patent and the range of motion required to operate the device with two hands (i.e., one hand on the device and one hand on the sliding hammer portion), the device is difficult to use in most limited work environments in which wedges must be installed in an anchor cavity. Additionally, as previously mentioned, when using the device disclosed in the '699 patent, the wedges tend to become prematurely separated from the tip of the device if the magnetic attraction is broken (e.g., if the wedges are bumped against the cable or other structure prior to installation) before the wedges are installed in the anchor. If the magnetic connection is broken, the wedges will fall from the device and need to be retrieved before the process can be started anew, which can be both time-consuming and frustrating.
Consequently, there exists in the art a long-felt need for a device or tool that enables a user to safely and properly install and seat wedges in an anchor assembly of a post tensioned concrete structure with a single hand, thereby freeing up the user's other hand. There is also a long-felt need for a device or tool that releasably secures the wedges to the tool until the same are properly installed in the wedge receiving seat of the anchor assembly. Additionally, there is a long felt need in the art for a single device or tool that properly installs and seats wedges in a post-tensioned concrete member, thereby eliminating the need for a separate seating tool which not only saves time but also reduces construction costs. There is also a long felt need for a quicker method of installing wedges in a post-tension concrete member that results in significant time, labor and cost savings, while also reducing the risk or likelihood of injury or death of the worker. Finally, there is a long-felt need for a device and method that accomplishes all of the forgoing objectives, and that is relatively inexpensive to manufacture, and easy to use.